High-vacua pump



R. BERRENBERG HIGH VACUA PUMP Filed Feb. ll, 1924 igpZ.

Patented May 4, 1926.

UNITED STATES BEINOLD BEBBENBEBG, F BOSTON, MASSACHUSETTS.

BIGH-VACUA PUMP.

Application led February 11, 1924. Serial No. 692,047.

f ducmg high vacua.

High vacua are finding a rapidly extending application in numerous branches of 1ndustry and it is highly important that eective means be provided for securing vacua. High vacua. are required for exhausting nitrogen lamp bulbs, vapor lamps, mercury are rectifiers, X-ray tubes, thermos bottles, etc.,

v and to be effective the pump must combine with a high capacity, a high limiting vacuum. A comparatively new field in which high-vacua pumps are necessary is radio, in which field the present invention is particularly efficient for evacuating the tubes used in that art for detect-ing and amplifying.

The object of the present invention is to provide a high-vacua pump of extreme simplicity of construction which is relatively cheap to manufacture and yet will produce and maintain a practically perfect vacuum.

In carrying out the object of the invention the type of pump selected is that embodying an eccentric rotor within the pump cylinder, two such pumps being connected in series, or tandem arrangement, so that what the first may lose the other takes up, and a single vane or abutment continuously engaging both rotors. By this means a final pressure of 0.0001 mm. of mercury, measured on a McLeod gauge, is readily obtained with a tandem pump the cylinders of which are only two inches in diameter.

To the accomplishment of this object and such others as may hereinafter appear as will readily be understood by those skilled in the art, the invention comprises the features and combinations of parts hereinafter described and then particularly pointed out in the appended claims.

The preferred form of the invention is illustrated in the accompanying drawings in which Figure 1 is a view, in side elevation, with the front cover of the tank removed, and Fig. 2 is a view, in vertical longitudinal section, through the center of the pump cylinders.

In the embodiment of the invention illustrated in the drawings an air tight tank 2 is provided having a removable cover (not shown) which tank, for convenience, may be provided with legs 6. Arranged centrally inside the tank on its bottom 4 is a rectangular boss 8 which has a finished upper surface to support the pump casing 10 which may be bolted thereon as shown.

The pump casing 10 comprises two cylindrical rotor chambers 12 and 14 both in one casting which forms a tangent, or Siamese, partition wall 15 between them. Within these chambers 12 and 14 are the rotors 16 and 18 respectively. Rotor 16 is mounted eccentrically on a. shaft 20 which is journaled in the front plate 22 and a rear plate (not shown). Rotor 18 preferably of like eccentricity is similarly mounted at the same angle as. rotor 16 on a shaft 24 which is journaled in the front and rear plates and is made long enough to extend through the rear wall 5 of the tank. The exterior portion of the shaft 24 carries a driving pulley belted to suitable power. Shafts 22 and 24 carry gears 26 and 28 respectively, outside the front plate 22,- the teeth of which mesh with the teeth of a central gear 30 which rotates idly on a stub shaft 32 carried by the front plate. The shaft 24 rotates in a manner to drive the rotor 18 in a clockwise direction and the gearing causes the rotor 16 to be driven in the same direction.

The tangent partition wall 15 is provided with a horizontal slot, the central plane of which lies in the plane of the axes of shafts 20 and 24, adapted to receive a sliding vane or rotor abutment having ends 34 and 36 engaging the circumferential surfaces of the rotors 16 and 1S respectively. The vane is formed in two parts and the meeting faces at substantially the center thereof are drilled to receive coiled expansion springs 3S which act to maintain an air tight contact between the vane and rotors at all times, in a wellknown manner.

The pump casing has a central boss 40 at its top which is cored during manufacture to produce the inlet and outlet ports indicated by the arrows a and b on Fig. 2. Below the rotor vane is a horizontal port c, formed in the same manner, connecting the rotor chambers 12 and 14.

' The pump casing is submerged, as usual,

in oil or other liquid, preferably a lubricant, and it is practically impossible to keep the oil from seeping into the rotor chambers. In order to prevent this entrapped oil from gathering in a sufiicient quantity to seal the ports through which the air is pumped, the port 0 is enlarged at its entrance, as

.shown at 42, by coring out the adjacent wall to the tank cover and, after passing therethrough, is joined to a tube 48 leading to the article to be evacuated, all as shown in Fig. 2. The tank is also provided with an opening 50, closed by a screw cap, through 'which the lubricant may be introduced and the air, discharged from the port b, permitted to escape.

The pump, in operation, draws the air from the article attached to the tube 48 which passes through port a and into the rotor chamber 12. Here it is forced through port 0 by rotor 16, the end 34 of the sliding vane compelling the air to travel around the rotor. The air is sucked through port 0 by the rotor 18 and forced by it through the outlet port Z) into the tank above the level of the oil bath. From here it may be removed at will, through the opening 50.

Particular attention is directed to the horizontal port 0 which, b v connecting the rotor chambers below the sliding vane, permits the series operation of the two rotors on the same body of air. Those skilled in the art will recognize at once the immensely greater efficiency of a tandem construction in which one pump supplements the other, over a supericially like construction in which the ports are so arranged that the two pumps operate alternately on different bodies of air. The extreme simplicity of construction will be apparent from the foregoing description, only three parts being required for each pump, i. e., the casing containing the cylinder, the rotor, and the rotor vane.

The nature and scope of the present invention having been indicated and the preferred embodiment of the invention having been specifically described, what is claimed as new, is

1. A tandem vacuum pump comprising a casing having two cylinders with a tangent partition wall between them, a rotor in each cylinder` a common rotor vane slidably seated in said wall, an inlet port for one pump and an outlet port for the other in said wall at one side of said vane, and a connecting port through said wall at the other side of said vane.

2. Vacuum pump apparatus comprising a tank, a pump casing within the tank having two cyiinders with a tangent partition Wall between them, a rotor in each cylinder, a common rotor vane slidably seated in said wall and a connecting port through said wall below the vane, said casing being substantally immersed in a liquid, andv having an inlet port leading to one pump cylinder above one end of said vane drawing from outside the tank, and an outlet portl leading from the other cylinder above the other end of said vane discharging within the tank above the level of the liquid, and means for driving both the rotors in the same direction.

3. A tandem vacuum pump comprising a casing having two rotor chambers with a common tangent partition wall each rotor being mounted on its own shaft, a common rotor vane slidably seated in said wall in the plane common to the axes of said shafts, means for driving both the rotor shafts in the same direction, and a series of ports in said tangent wall for causing the air drawn into one rotor chamber to be forced by the rotor therein into the other rotor chamber and then be discharged by the second rotor,

4. A tandem vacuum pump comprising a casing having two cylinders with a tangent partition wall between them, a rotor in each cylinder, ya common rotor vane slidably seated inysaid wall, an inlet port for one `pump and an outlet port for the other at one side of said vane, and a connecting port through said wall at the other side of said vane, said casing being enclosed in a tank and substantiallyimmersed in oil and the entrances to said connecting and outlet ports being enlarged to permit free passage of entrapped oil through the pump.

5. A tandem vacuum pump comprising a casing having two rotor cylinders with a common tangent partition wall, a. shaft in each cylinder having a rotor mounted thereon, the angle of the eccentricity of said rotors on their shafts being equal, a common, diametrically arranged sliding vane between said rotors composed of two parts each of which is yieldingly held in constant engagement with its respective r0- tor, ports formed in said wall above and below said vane permitting the same quantity of air to enter one cylinder from one side of said vane, pass through the partition wall at the other side of said vane and then out of. the casing at saidffirst side of the vane, and means for driving both rotor shafts in the same direction.

6. A casing for rotary vacuum pumps adapted to be substantially submerged in an oil bath, having a cylindrical chamber for receiving the rotor, and air inlet and outlet ports leading to said chamber through the wall thereof, said wall being cupped about the end of said outlet port to prevent sealing by entrapped oil.

A rotary vacuum pump casing com rising a casting having two rotor cham rs with a common tangent wall between them, said wall being slotted through transversely at its central portion, said wall having also a port extending transversely therethrough at one side of said slot, and two independent orts formed within said Wall each extendmg longitudinally thereof from the outer surface of the .casting and then turning in la port through said wall at the other side 86 of said vane means.

REINOLD BEBRENBEBG.

between them, a rotor in each I0 

